Thematically it would've worked better had Picard been the one to die.

1. It would've worked better with the story they were going for. King Arthur meets his long lost son Mordred. In the story Mordred strikes down Arthur as Arthur pierces him with a lance. Displayed in how Picard ends Shinzon.

2. Also had Picard died then Riker would likely been promoted to captain of the Enterprise. The rest of the crew would've stayed together after that. Worf and Geordi never left the Ent-E, Troi now Riker's wife wouldn't leave for the Titan, Crusher may have stayed on to keep the family together and Data would be first officer.

3. Riker's destiny would be fufilled by becoming captain of the Enterprise. There mission would be working on relations with the Romulans just like at the end of NEM. Mirroring Undiscovered Country by making a long time enemy an ally.

Timo wrote:

Picard or Shinzon, with the audience left wondering.

That is, have Stewart portray both characters (at least after Shinzon's weird biological processes reach their peak - Tom Hardy until then is fine with me), have the big fight between the two in the end, and have a person looking like Stewart sacrifice his life in order to stop the evil thing (loss of E-E, or perhaps loss of Earth) from happening, while another person looking like Stewart survives, walks away from the carnage, and sits in Picard's chair. Did Picard triumph, or did Shinzon realize how wrong he had been, have a change of heart, and finally assume the role he was destined for - that of replacing Picard?

Everybody expected Baird to pull a Gladiator with this story; that's why he was asked to do the gig the first place. A happy ending involving the death of the hero would be right up his alley, and what was expected, but with enough of a surprise twist to satisfy the audience.